Two-stage control throttle mechanism



NOV. 4, 1969 Hrr ET AL TWO-STAGE CONTROL THROTTLE MECHANISM 2 Sheets-Sheet 1 Filed Feb. 21, 1966 INVENTOR.

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Nov.'4, 1969 o. D. HlTT ETAL 3,476,147

I TWO-STAGE? CONTROL THROTTLE MECHANISM Filed Feb. 21. 1966 2 Sheets-Sheet 2 INVENTQR.

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BY Z Srmvnta Qvur United, States Patent U.S. Cl. 137614.14 Claims ABSTRACT OF THE DISCLOSURE A two-stage control throttle mechanism for motordriven screw drivers and the like permits initial maximum flow of power to the motor for overcoming inertia, and upon further depression of a control trigger permits throttling to a lower speed controlled 'by the position of the trigger, so that the motor can stall at low power, thereby providing a predetermined torque at the final position of the screw.

This invention relates to a two-stage control throttle mechanism wherein a first stage of trigger action for a pneumatic tool or the like opens a control valve for maximum fluid flow to the motor and a second stage of trigger action (further depression of a finger operated trigger) reduces the opening through a throttle valve so that reduced speed and torque are thereupon had.

A two-stage control throttle mechanism of the kind herein disclosed is particularly designed to drive selfdrilling and self-tapping fasteners such as screws or the like wherein high speed and torque are required for the drilling operation but a low speed for the tapping operation is desired terminated by low stalling torque to prevent the screw from being twisted off or seated too tightly, and to prevent the dimpling of sheet metal around the head of the screw because of too' much stalling torque.

One object of our invention is to provide a comparatively simple and inexpensive valve structure incorporating both a control valve and a throttlevalve wherein the valve seats are in fluidic series and the control and throttle valve elements are in mechanical series whereby a trigger or the like may be utilized to operate the twovalves simultaneously in such manner that partial depression of the trigger permits full fluid flow whereas complete depression of the trigger throttles the flow in such manner that the stall torque of the fluid operated motor is much less than the initial torque used for the drilling operation. The stall torque thereby determines the tightness of the screw and prevents overtightening.

Another object is to provide an arrangement of valve elements and valve seats wherein a control valve element is normally seated on a control valve seat and a throttle valve element is normally spaced from a throttle valve seat, the trigger action controlling the unseating of the control valve element by spacing it from the control valve seat for maximum fluid flow through both valve seats, and upon further spacing of the control valve element from the control valve seat causing the throttle valve to approach the throttle valve seat to reduce fluid flow through both valve seats.

Still another object is to provide the trigger with a maximum control position which determines the minimum throttling position of the throttle valve element relative to the throttle valve seat.

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A further object is to provide means to predetermine the maximum spacing of the control valve element relative to the control valve seat, the spacing of the throttle valve element from the control element being variable to predetermine the minimum throttling position of the throttle valve element relative to the throttle valve seat.

Still a further object is to provide means for adjusting the spacing of the throttle valve element from the control valve element to change the minimum throttling position of the throttle valve element relative to the throttle valve seat at maximum trigger position.

An additional object is to provide a modified form of the invention in which a pair of springs are provided for the trigger, one to bias it to its normally inoperative position and the other to resist its further movement upon it assuming an intermediate position in which there is maximum fluid flow, thereby requiring a certain finger pressure for maximum fluid flow and a greatly increased finger pressure for throttling action.

With these and other objects in view, our invention consists in the construction, arrangement and combination of the various parts of our two-stage control throttle mechanism, whereby the objects above contemplated are attained, as hereinafter more fully set forth, pointed out in our claims and illustrated in detail on the accompanying drawing, wherein:

FIG. 1 is a vertical sectional view through the handle of a pneumatic motor in which our two-stage control throttle mechanism is mounted, a reversing valve and a pneumatic motor being shown diagrammatically, the figure also illustrating a self-drilling and self-tapping screw associated with the motor, the control throttle mechanism being in normal or inoperative position;

FIG. 2 is a sectional view similar to a portion of FIG. 1 showing the control throttle mechanism in maximum fluid flow position;

FIGS. 3 and 4 are sectional views on the lines 33 and 44 of FIG. 1;

FIG. 5 is a sectional view similar to FIG. 2 showing the control throttle mechanism in throttling position;

FIG. 6 is a similar sectional view showing the throttle valve of FIG. 5 adjusted to a different position relative to a control valve, and

FIG. 7 is a sectional view similar to a portion of FIG. 1 showing a modification in the trigger mechanism for actuating the control throttle mechanism.

On the accompanying drawings we have used the reference numeral 10 to indicate, in general, the handle of a pneumatic motor shown diagrammatically at 12. A motor shaft 14 extends from the motor 12 and terminates in a chuck 16 for a suitable tool 18 such as a screwdriver bit. The tool 18 is shown cooperating with the head of a screw 20 having a self-drilling portion 22 and a self-tapping portion 24.

Our valve mechanism includes a valve sleeve 26 mounted in a bore of the handle 10 and terminating in a control valve seat 28. A control valve element 30 has an O-ring 32 adapted to normally seat against the seat 28 due to the pressure of air below the seat as will hereinafter appear. A valve stem 34 extends from the control valve element 30 and is slidable in the sleeve 26, its upper end being actuated by a trigger 36. The trigger 36 is slidable in another bore of the handle 10 and is normally biased to the position shown in FIG. 1 by a trigger spring 38. A stop 40 coacts with a stop notch 44 in the trigger to limit the normal position and also a maximum operative position as will hereinafter appear. The stop 40 is retained in position by a stop screw 42 as shown in FIG. 3. The trigger 36 is provided with an inclined face 46 coacting with the upper end of the valve stem 34 for sliding the valve stem in the sleeve 26 in response to sliding action of the trigger in its bore of the handle 10.

A throttle valve sleeve 48 is also provided in the handle and has a throttle valve seat 50 opposite which is a throttle valve element 52. The throttle valve element is normally spaced from the seat 50 as shown in FIG. 1 and is adjustably mounted on a threaded portion 54 of the valve stem 34 for adjusting purposes as will hereinafter appear. To retain the adjustment, a ball 56 of nylon or the like is squeezed between the bottom of a drilled hole 58 and the threads of the portion '54.

The sleeve 48 is retained in assembled position by a nipple 60, suitable O-ring seals being provided as illustrated, and the nipple may have a compressed air hose or the like (not shown) connected therewith to supply fluid pressure to the motor 12. The nipple 60 is also removable for the purpose of permitting adjustment of the throttle valve element 52 on the threaded portion 54 of the valve stem 34, the sleeve 50 and the assembly 34, 30, '54, 52 being thereupon removable from the bore in the handle 10 and from the sleeve 26 to permit changing the adjustment.

A modified construction is shown in FIG. 7 wherein a comparatively light trigger spring 38 is substituted for the spring 38 of FIG. 1 and a relatively heavy trigger spring 62 is also provided as an aid to proper operation of the trigger 36 as will hereinafter appear.

PRACTICAL OPERATION In the operation of our two-stage control throttle mechanism for the purpose of driving screws of the type shown in FIG. 1, or for any other purpose where twostage operation is desired, the trigger 36 may be depressed from the position indicated a in FIG. 1 about half way to the position b shown in FIG. 2 whereupon the control valve element is sufficiently spaced from the control valve seat 28 to provide maximum fluid flow (heavy arrows in FIG. 2) and accordingly the required motor speed and torque for rotating the screw so that its drill portion 22 will drill through the sheet metal or other material being fastened together. As soon as the operator observes that the drilling operation has been completed, he depresses the trigger 36 all the way (position 0 as shown in FIG. 5) which opens the control valve 28, 30 wider but this has no effect as the throttle valve element 52 is now more closely spaced to the throttle valve seat 50 and thus throttles or meters the flow of fluid as shown by the medium weight arrows. The minimum throttling opening between the seat 50 and the valve 52 is thus predetermined by the trigger 36 being fully depressed. Accordingly, the screw 20 is driven home until the motor 12 stalls but the stalling torque is now much less than when the throttle mechanism is in the position of FIG. 2, and accordingly does not overtighten the screw but tightens it with a predetermined torque which avoids the dimpling of the metal around the head of the screw as experienced when screws are overtightened.

For lighter screws the torque can be effectively reduced in the maximum operative (FIG. 5) position of the trigger 36 by adjusting the valve element 52 farther down on the threaded portion 54 of the valve stem 34 as shown in FIG. 6. The flow of air is now indicated by light weight arrows to illustrate less stall torque of the motor 21.

An operator using our two-stage control throttle mechanism soon acquires the necessary skill to depress the trigger 36 about half way (position b) for drilling purposes and to change to full depression (position c) at the proper time to secure the stalling torque determined 4 by the throttle valve 50, 52 in the position of FIG. 5 (or FIG. 6).

As an aid to proper operation of the trigger, the modification shown in FIG. 7 may be utilized wherein initial depression from position a to position b is about half the stroke of the trigger and at that point depression of the trigger is resisted by the heavier spring 62. This serves to indicate to the operator through the increase in opposition to finger pressure on the trigger that the half way position has been reached, and at the proper time he squeezes the trigger hard to move it to position 0 and pushes forwardly on the handle 10 with increased pressure to cause the threads 24 of the screw 20 to thread the sheet metal parts being fastened together and move into seated position until the motor stalls whereupon the trigger is released and the tool moved on for the next screw-setting operation.

Some changes may be made in the construction and arrangement of the parts of our two-stage control throttle mechanism without departing from the real spirit and purpose of our invention, and it is our intention to cover by our claims any modified forms of structure or use of mechanical equivalents which may reasonably be included within their scope.

We claim as our invention:

1. In a fluid motor operated device the improvement of a two-stage control throttle mechanism comprising, in combination, valve sleeve means having a fluid inlet and a fluid outlet, a control valve seat adjacent said outlet in said sleeve means, and a throttle valve seat adjacent said inlet in said sleeve means, said seats being in fluidic series and opening toward each other, a control valve element seatedon said control valve seat when said mechanism is in an inoperative position and a throttle valve element spaced from said throttle valve seat when said mechanism is in an inoperative position, said valve elements being constructed and arranged to seat away from each other, a mechanical connection for connecting said valve elements together in series and means for unseating said control valve element by spacing it from said control valve seat while said throttle valve element is held also spaced from said throttle valve seat by said mechanical connection, said means for unseating including a pair of springs, one of said springs to bias said control valve elements into said inoperative position to prevent fluid flow and the other of said springs to resist movement of said means for unseating whenever said means for unseating assumes an intermediate position, said intermediate position being that position of maximum fluid flow through said mechanism, said other spring maintaining said bias through a maximum operative position said maximum operative position being a position wherein flud flow is less than the maximum fluid flow.

2. The improvement according to claim 1 wherein both the maximum spacing of said control valve element relative to said control valve seat and the minimum spacing of said throttle valve element from said control valve element are adjustable by varying the length of said mechanical connection.

3. The improvement according to claim 1 wherein said means for unseating comprises a finger operable trigger having a normally inoperative position and movable to a maximum operative position determined by said stop means, said trigger in an intermediate operative position moving said valve elements to their positions for maximum fluid flow, and in maximum operative position effecting said reduction of fluid flow through said throttle valve to thereby effect a predetermined throttling action.

4. The improvement according to claim 1 wherein the maximum control position of said means for controlling determines the minimum throttling position of said throttle valve element relative to said throttle valve seat.

5. The improvement according to claim 4 wherein the spacing of said throttle valve element from said control valve element is adjustable to change the minimum throttling position of said throttle valve element relative to said throttle valve seat.

References Cited UNITED STATES PATENTS 1,858,164 5/1932 May 251--211 2,659,197 1/1953 Halford 251211 WILLIAM F. ODEA, Primary Examiner 5 HOWARD M. COHN, Assistant Examiner Bremer 137-614.14 XR Farrell 137614.14 XR Pomeranz.

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